1. Field of the Invention
The present invention relates to a film forming apparatus and a film forming method.
2. Related Background Art
In forming films of, for example, metals, alloys, polymers and ceramics on substrates, physical vapor deposition (PVD) as exemplified by sputtering and evaporation and chemical vapor deposition (CVD) energy such as electrical discharge, heat or light have been hitherto usually utilized.
When films are formed using these processes, deposits, which are produced by deposition of a film forming material, can not be perfectly prevented from being formed on the surface of an inner wall of a film forming chamber in addition to the authorized formation of films on the substrates. Such deposits increase in thickness each time the film formation is repeated, and tend to cause film peel-off because of their own internal stress when they reach to a certain thickness. This film peel-off generates fine dust in the film forming chamber (i.e., dusting), so that the film in the course of formation attracts the above fine dust causing a lowering of the film quality because of the formation of spherical protuberances or the like.
To prevent this dusting, there is a method in which the deposits formed on the inner wall of a film forming chamber are removed by etching or the like after the film formation is completed (Japanese Unexamined Patent Publication (Kokai) No. 59-142839 (1984)). There is another method in which a film forming chamber is equipped in its inside with plate-like materials, called deposit shield plates, capable of preventing the deposits from being formed on the inner wall surface of the film forming chamber (Kobayashi et al., "SHINKU (Vacuum)", Vol. 28, No. 5, pp. 184-186, 1985).
However, the method in which the deposits are removed by etching or the like has had the problems, for example, in that it shortens the life of apparatus depending on what kind of material is used in the members disposed inside the film forming chamber, it is difficult to ascertain the completion of the removal of deposits, and it takes a long time for removal of the deposits.
On the other hand, the method in which the film forming chamber is equipped on the inside with the deposit shield plates as shown in FIG. 1 has the advantage that the film can be readily prevented from being contaminated without shortening the life of the apparatus, since the deposit shield plate is changed for new one on which no deposits that may cause dusting are adhered, before the substrate or the film in the course of formation is contaminated by dusting. However, as illustrated in FIG. 1, when a set of deposit shield plates is changed for new one, the respective deposit shield plates are unfastened one by one, so that the film forming chamber must be widely opened.
An example of the manner in which the deposit shield plates are disposed is described below with reference to FIG. 1.
FIG. 1 is a schematic view which diagramatically illustrates how the deposit shield plates are disposed in a conventional typical film forming apparatus. In FIG. 1, the numeral 1 denotes a deposit shield plate for the innermost wall surface of a film forming chamber 11; 2, a deposit shield plate for the right side wall surface; 3, for the left side wall surface; 4, for the ceiling wall surface; and 5, for the front side target wall surface. The numeral 6 denotes a holder, holding a substrate (a disc substrate) on which films are formed, which holder is come down by rotating a shaft portion 12 toward the innermost wall side until it comes to a horizontal state, where it holds the disc substrate carried from an open gate (not shown) and is turned to an upright position (in the state shown in FIG. 1) until it faces a target 16, and film formation is carried out in that state on the substrate. The numeral 7 denotes an auxiliary deposit shield plate fixed in the electrical discharge space so that the film deposition on the the substrate holder 6 can be suppressed to a minimum; and 8, a deposit shield plate for the bottom surface of the film forming chamber. The numeral 13 denotes a nut to fasten each deposit shield plate.
Under such construction, the inner wall of the film forming chamber 11 is exposed to air and hence the gases such as nitrogen, oxygen, carbon dioxide and water contained in the air are adsorbed on the inner wall of the film forming chamber 11, so that it has sometimes occurred that it takes a long time until the inside of the film forming chamber 11, when evacuated after the deposit shield plates have been changed, reaches the desired vacuum degree before the film formation is again started.
It has also sometimes occurred, for example, that the surfaces of targets such as metals, polymers or ceramics, or film forming starting materials such as vapor deposition starting materials undergo chemical reaction such as oxidation to cause compositional changes of the film forming starting materials, resulting in compositional changes of the film to be formed. Hence, for the purpose of forming films with the desired composition after the deposit shield plates are changed for new ones, it has been sometimes required to provide a treatment, for example, to remove by sputtering the surfaces of targets having undergone compositional changes or to remove by evaporation the vapor deposition starting materials.
Thus, changing the deposit shield plates for new ones has caused a decrease in the compositional uniformity of films and the operating efficiency of the film forming apparatus.